1. Field Of The Invention
The present invention generally relates to a refrigerant compressor and, more particularly, to a slant plate type compressor, such as a wobble plate type compressor, with a variable displacement mechanism suitable for use in an automotive air conditioning system.
2. Description Of The Prior Art
A wobble plate compressor with a variable displacement mechanism suitable for use in an automotive air conditioning system is disclosed in U.S. Pat. No. 3,861,829 to Roberts et al. As disclosed therein, the compression ratio of the compressor may be controlled by changing the slant angle of the inclined surface of the wobble plate. The slant angle of the inclined surface of the wobble plate changes in response to a change in the crank chamber pressure. Changes in the crank chamber pressure are generated by a valve control mechanism which controls communication between the suction chamber and the crank chamber.
The relevant part of an additional prior art compressor is shown in FIGS. 1a and 1b. Drive shaft 1 includes groove 2 located near one end thereof. Split ring return spring 3 is fixed in groove 2 by snap portion 4. When the slant plate reaches its minimum or zero slant angle, it is contacted by split ring return spring 3 which urges it back towards greater slant angles. However, since split ring return spring 3 is not firmly fixed within groove 2, it may fall off during rotation of the drive shaft. Additionally, split ring return spring 3 occupies a large radial space around drive shaft 1, and thus has a tendency to interfere with other internal parts of the compressor.
Additionally, if a bias spring were used in place of the split ring return spring with the grooved drive shaft shown in FIGS. 1a and 1b, and no provision for firmly securing the bias spring to the drive shaft is made, the bias spring may move along the drive shaft during rotation thereof. Thus, the bias spring may become fixed at an undesirable location on the drive shaft and may therefore prevent the slant plate from pivoting to freely assume various slant angles. Accordingly, the variable displacement function of the compressor may be ineffective.